The overarching goal of the Transdisciplinary Research Methods (Methods) Core is to support and train investigators in the use of appropriate research methodology to strengthen the evidence base for HIV and other infectious disease prevention and care strategies for substance users (SUs), and to embed effective strategies into routine practice. The theme for CDUHR IV of Research Translation has guided the formulation of our Core's aims and the organization of this Core narrative. Thus, the Methods Core's Aims 1-4 address phases in the Research Translation Cycle: Discovery of emerging issues. Synthesis with existing knowledge, Intervention design and testing, and Implementation of evidence-based practices. Figure 1 illustrates the Research Translation Cycle, showing how the Core will focus on research synthesis, broadly conceived, as a crucial step in transitioning from one phase in the cycle to another. While research synthesis methodologies can be used throughout the cycle, this Core will focus primarily on research synthesis in the earlier phases (I.e., from discovery to intervention design); research synthesis utilized in later stages (i.e., to make funding decisions regarding implementation and to assess public health impacts), will be the focus of the CER Core.